doneit-web/src/app/services/theme.service.ts

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class ThemeService {

  themes = [
    'gov',
    'default'
  ]

  currentTheme = 'gov'

  constructor() { }

  setTheme(theme: 'gov' | 'default') {

    document.body.classList.remove("gov");
    document.body.classList.remove("default");
    document.body.classList.add(theme);
    this.currentTheme = theme

  }

}